This work will improve the definition of limitations to hearing aids caused by feedback and/or occlusion effects and will continue the development and clinical verification of the usefulness of a minimum contact earpiece with a disposable foam seal to reduce the occlusion effect and jaw motion induced feedback. The definition will be accomplished with physical characterization of subjects' ear canals and the use of an addendum to a common profile of hearing aid performance. A thorough study of the cartilaginous region is planned, using silicone ear impressions at closed and wide-opened jaw positions. A high-speed laser reader will automate data collection. The profile will initially be designed with experts in its use and refined throughout the study. The earpiece is designed to be inserted slightly deeper than usual, to near the end of the cartilaginous region of the canal. After development of practical techniques to produce the earpiece and disposable foam seal, well-controlled clinical measures will quantify the objective and subjective reduction in feedback and/or occlusion. Following mass production of the disposable foam seal, a study of patient preference, as well as benefits and limitations of the earpiece, will be undertaken at four clinical sites. PROPOSED COMMERCIAL APPLICATION: The earpiece resulting from this research is intended to increase hearing aid performance by significantly reducing the occlusion effect and jaw motion induced feedback. It is applicable to three million existing hearing aid wearers in the U.S. and to a majority of new ones. It is potentially useful with assistive listening devices, stethoscopes, and telephone headsets.